1. Field of the Invention
The present invention relates to a label manufacturing method and a label manufacturing apparatus for manufacturing a label made of a heat sensitive adhesive sheet having a heat sensitive adhesive layer formed on a single side of a sheet-like substrate, which normally exhibits no adhesive properties but develops adhesive properties when being heated.
2. Description of the Related Art
Conventionally, a heat sensitive adhesive sheet having a heat sensitive adhesive layer that develops adhesive properties when being heated has been commercialized. Such a heat sensitive adhesive sheet as described above has advantages that the sheet before being heated can be handled easily because the sheet does not have the adhesive properties and that the heat sensitive adhesive sheet does not need release paper and industrial waste is thus not produced. Further, this label made of the heat sensitive adhesive sheet is attached onto various articles and is used in many fields such as a display like a bar code or the like for a point of sale (POS) of products such as foods, a shipping tag for distribution and delivery, a baggage tag in a hotel or a vehicle, or a display of contents of a bottle, a can, a cartridge or the like.
In general, the heat sensitive adhesive sheet is transported while heating means heats the heat sensitive adhesive layer to develop adhesive properties, whereby a desired label is manufactured. In order to heat the heat sensitive adhesive layer of the heat sensitive adhesive sheet, a thermal head that is commonly used as a recording head of a thermal printer is used as the heating means in many cases (see Patent Documents JP 2004-243606 A and JP 2004-136972 A). In this case, the heat sensitive adhesive layer of the heat sensitive adhesive sheet is pressed to the thermal head while the heat sensitive adhesive sheet is transported, whereby an entire surface of the heat sensitive adhesive layer or a part thereof is thermally activated to develop adhesion.
When the heat sensitive adhesive sheet is transported while the heating means is operated to heat the heat sensitive adhesive layer to be thermally activated as described above, a period of actuating the heating means is determined based on a desired label size. More specifically, operation of the heating means is stopped substantially at the same time when a trailing end portion of the heat sensitive adhesive sheet has passed through a position contacting with the heating means.
In a conventional label manufacturing method, as shown in FIG. 12, heating of a heat sensitive adhesive sheet 2 is performed until a trailing end portion 2b in a transporting direction of the heat sensitive adhesive sheet 2 passes through a position contacting with a heat-generating portion 4a of a thermal head 4 as described above, a problem may occur in some cases that a heat sensitive adhesive 2e at the trailing end portion 2b of the heat sensitive adhesive sheet 2 adheres to the thermal head 4 (see FIG. 12). Specifically, the heat sensitive adhesive 2e disposed on the heat sensitive adhesive sheet 2 is heated at a portion contacting with the heat-generating portion (heating element) 4a of the thermal head 4 and is thermally activated so as to develop adhesive properties. The heat sensitive adhesive 2e that is developing adhesive properties is in the state where the heat sensitive adhesive 2e can easily adhere to the thermal head 4. Usually, even if the heat sensitive adhesive 2e with the developed adhesive properties tends to adhere to the thermal head 4, the heat sensitive adhesive 2e is peeled away from the thermal head 4 as the heat sensitive adhesive sheet 2 is transported. Then, the heat sensitive adhesive 2e is only moved to the trailing end side of the heat sensitive adhesive sheet 2 a little by being dragged by the thermal head 4 in some degrees, and is carried away by the heat sensitive adhesive sheet 2. However, as illustrated in FIG. 12, at the trailing end portion 2b of the heat sensitive adhesive sheet 2, if the heat sensitive adhesive 2e with the developed adhesive properties is dragged by the thermal head 4 even in some degrees, the heat sensitive adhesive 2e is pushed off the heat sensitive adhesive sheet 2. Then, the pushed-off heat sensitive adhesive 2e does not sufficiently receive a force accompanying the transporting of the heat sensitive adhesive sheet 2, whereby the heat sensitive adhesive 2e may adhere to the thermal head 4 and remain thereon. If the manufacturing of the label is repeated, the heat sensitive adhesive 2e adhering to and remaining on the thermal head 4 as described above may be accumulated, which may be a factor of preventing smooth transporting of the heat sensitive adhesive sheet 2. Therefore, if many labels are manufactured, it is necessary to perform a maintenance work for cleaning the thermal head 4 so as to remove the heat sensitive adhesive 2e adhering to the same. This maintenance work prevents continuous manufacturing of many labels and decreases the efficiency.